Steel has been manufactured for many years using variations of a conventional process in which iron ore and limestone are combined with coke and added continuously to a blast furnace where preheated air is added to facilitate combustion and create high heat. From the blast furnace, impurities are removed as slay and iron with a high carbon content is removed as molten metal. The molten iron is then further refined in a bessemer furnace, basic oxygen furnace, open hearth furnace or electric arc furnace (depending on the newness of the plant and the quality of steel required) where excess carbon is removed and additives which effect the quality of steel are combined with the molten iron. The molten steel is drawn off in batches and thereafter processed by rolling it into bars, pipes, plates, sheets, rails or structural shapes.
Although variations of this process are used to handle different types of ore or to produce different types of steel, the basic process has remained substantially unchanged for many years.